To multiply 0.3 × 0.4, multiply the digits as whole numbers: 3 × 4 = 12. Count the decimal places in both numbers. 0.3 has one and 0.4 has one, which makes two in total. So the answer has two decimal places: 0.12.
This makes sense: 0.3 × 0.4 means three tenths of four tenths, which is a small amount. When you multiply by a number less than 1, the answer is smaller than the number you started with.
Worked example
1.2 × 0.5 =
- 12 × 5 = 60.
- There are two decimal places in total, so 0.60.
Answer:0.6
Key words
- total decimal places
- the decimal places in both numbers added together
- product
- the answer to a multiplication
- less than 1
- makes the answer smaller
Practise this
New questions every time.
Common Core-referenced: 5.NBT.B.7